Abstract: Redox behavior and electrocatalytic activities of the Ti/nano-TiO₂ electrode were investigated by cyclic voltammetry(CV) and bulk electrolysis. The results indicate that there are two pairs of well-defined redox peaks for Ti/nano-TiO₂ film electrode in the 1 mol/L H₂SO₄ and 1 mol/L NaOH at 0.1 V/s corresponding to TiO₂/ Ti₂O₃ and TiO₂/Ti(OH)₃ reversible electrode process. In 1 mol/L NaOH medium the peak potential evidently shift to the negative value with E_1/2^r being -1.38 and -1.72 V(vs.SCE), and the heterogeneous electrocatalytic reduction activities of TiO₂/Ti₂O₃ redox for p-nitrobenzoic acid (PNA) is very high. The indirect electroreduction of PNA to p-aminobenzoic acid (PAA) by Ti^Ⅳ/Ti^Ⅲ redox system on nanocrystalline TiO₂ film surface was found, and the electrode reaction mechanism is called electro-catalytic(EC) mechanism. In the preparative electrolysis, the current efficiency was over 90%.

Key words: Nanocrystalline TiO₂ film electrode, Electrocatalysis, Cyclic voltammetry, p-Nitrobenzoic acid, p-Aminobenzoic acid